1. Field of the Invention
The present invention relates to a wire cutting electric discharge machine, and, in particular, to a wire cutting electric discharge machine of the type wherein the electric discharge machining is performed with the workpiece immersed in a process liquid.
2. Description of the Prior Art
As is commonly known, a conventional wire cutting electric discharge machine is provided with an upper and a lower wire guide devices respectively supported on the free ends of the upper arm and the lower arm, which are separated in the vertical direction. Each of the wire guide devices comprises a guide section which guides a wire electrode in the axial direction and an electrical section which supplies electricity to the wire electrode.
Each of the wire guide devices further comprises a nozzle for feeding a process liquid into a processing gap between a workpiece and the wire electrode.
Conventionally, the nozzle is formed with a circular nozzle opening with straight sides at a uniform diameter so that no vibration is imparted to the wire electrode from the turbulent flow of the process liquid when the process liquid is being supplied from the nozzle (for example, as disclosed in Japanese Laid Open Publication No. 57-227691). This nozzle may work well when the process liquid is fed from the nozzle at a comparatively low pressure (several kg/cm.sup.2).
In recent years, however, the process liquid is fed at high pressure (several tens of kg/cm.sup.2). Under such high pressure, the turbulent flow easily occurs even with the nozzle of the prior art. This is because there are discontinuous points on the open end of the nozzle.
In particular, in the prior art, since the cross-sectional shape and the cross-sectional area close to the open end of the nozzle are uniform, considerable turbulent flow occurs, mainly at the discontinuous points, giving rise to an irregular feeding operation.
This presents a problem from the aspect of improving processing precision.